This invention concerns a mattress system, including either a mattress or a mattress overlay with support surface features for reducing shear stress to the skin of a person received thereon.
In medical care, the prevention of decubitus ulcers to the skin of non-ambulatory persons remains a goal. Also known as “bed sores” and “pressure ulcers,” decubitus ulcers may result in part from physiological causes such as decreased circulation, reduced skin integrity, impaired nutrition, and other bodily weaknesses. Certain areas of the body have been observed to have a relatively greater tendency to develop decubitus ulcers, including the spine, hips, buttocks, elbows, and heels. Conversely, certain portions of the body have been observed to have a relatively lesser tendency for the development of decubitus ulcers, such as the thigh area in which greater blood flow, the absence of bony prominences, and larger weight-bearing surfaces may be found.
In addition to physiological causes, external factors may contribute to the development of decubitus ulcers. Localized pressure to the skin is one such factor. Pressure to the skin occurs from support by the mattress system of the person's weight. Because different portions of the human body have different weights and have different surface areas for distribution of that weight upon a mattress, different pressure can be brought to bear at various locations along a person's body, with localized points of relatively great pressure. Of course, a generally planar mattress surface, supporting the very non-planar human body, will result in even smaller areas of support, with concomitant greater increase in the pressure upon those areas.
Another external cause that may exacerbate the development of decubitus ulcers is moisture from perspiration, which makes the skin softer and more tender. As a person lies on a bed, perspiration from skin in contact with the bedding surface may tend to accumulate rather than fully evaporate. By remaining in contact with the skin, the perspiration softens the skin and makes it more susceptible to breakdown, and thereby more susceptible to decubitus ulcers.
Still a third external exacerbation of the tendency of decubitus ulcer development is shear stress upon the skin. Shear stress occurs, in part, from the friction of rubbing the surface of the skin. For the bed-bound person, shear most often occurs specifically between the person's skin and the bed linens upon the mattress. However, the degree and extent of that shear stress is influenced by the surface features of the mattress or padding beneath the bed linens. For example, a button sewn to the fabric surface of a conventional mattress may not itself come in direct contact with the skin of a person lying upon the mattress if the mattress is covered with a sheet. However, that button may greatly increase the shear upon the skin of a person moving upon the sheets over the button, as it is an irregularity that would be felt through the sheets. Some shear stress to the skin of a person reclined upon a bed may be unavoidable, as some movement upon bedding is natural and in fact often is medically preferred. However, the presence of unnecessary irregularities projecting even slightly from the surface of a mattress may needlessly increase the opportunity for and the degree of unwarranted and damaging shear stress to the skin.
The problem of shear stress to a person's skin is further complicated by the fact that nonambulatory persons may benefit from having the head portion of their bed system raised. A raised head portion may improve blood flow and digestion, may promote beneficial social discourse with and entertainment of the bed-bound person, and facilitates eating and the oral administration of drugs. However, the raising of the head of the bed also results in gravitationally-generated shear stress upon the skin of the person, as the person's body is forced downward along the inclined slope of the mattress surface, generating shear stress against the mattress surface.
To combat the development of decubitus ulcers, the medical practice has employed the use of foam mattresses, or foam overlays upon conventional mattresses, for non-ambulatory persons and others at risk of such problems. Such foam products often include cuts or slices upon their surface so as to more greatly disperse localized pressure upon areas of the body, and also to better allow for ventilation of collected perspiration for drying of the skin. However, while addressing pressure and moisture as contributors to the development of decubitus ulcers, such products have not optimally reduced shear upon the skin as another contributor, and particularly have not addressed the increase in shear stress caused by elevation of the head of the bed.